The bleaching, or whitening, of teeth is a subject of much current interest in the dental community. Besides the pleasurable effects of white teeth, discoloration of non-vital teeth is often a consequence of endodontic treatment or in traumatized teeth which have experienced a loss of pulpal vitality. Vital teeth may become stained due to tetracycline prescribed for the patient for various medical reasons. Other causes of stained teeth may be drinking water with a high mineral content, caffeine drinks, and the use of tobacco products. Stains caused by these materials are not always removable by conventional prophylactic treatment. Conventional cleaning includes tooth brushing and/or the use of dental rinses.
There has been much recent interest in dentistry to whiten teeth. As discussed in Reality, The Information Source for Esthetic Dentistry 1996 edition, the available types of bleaching materials can be classified into three categories. These categories are power bleaching, assisted bleaching, and home bleaching.
Power bleaching materials contain high concentrations of hydrogen peroxide or other source of active oxygen. Most dental bleaches are applied as gels or pastes which are freshly prepared as needed in the dental operatory. Since hydrogen peroxide is a liquid, a powder is mixed with it for thickening. There may also be other ingredients present, such as catalysts or indicators. Light or heat is usually part of power bleaching.
In U.S. Pat. No. 5,240,415, Haynie discloses a dental bleaching system with separately compartmented hydrogen peroxide and fumed silica. Haynie is concerned with trays and storage compartments for the peroxide and carrier. There is no mention of any substances other than hydrogen peroxide and silica for bleaching. There is also no mention of heat or light in the bleaching process.
U.S. Pat. No. 5,645,428 to Yarborough utilizes peroxide mixed with a first catalyst applied to the tooth, after which the tooth is exposed to light from an argon laser. Next, a mixture of peroxide and a second catalyst are again applied to the tooth and irradiated with a carbon dioxide laser. This method employs a variety of other ingredients, including buffers, desensitizers, thickeners and the like. It also mentions the use of magnesium sulfate as a photocatalyst. There is no component of this bleaching composition with provides a distinct color change when the bleaching process is complete for that tooth.
A non-laser method for bleaching stained teeth by applying a concentrated solution of peroxide to stained teeth and focusing a beam of light at the teeth has been patented by Friedman in U.S. Pat. No. 4,661,070. The focused beam contains the combination of ultraviolet and infrared energy for activating the peroxide solution. There is no other chemical substance besides hydrogen peroxide in the Friedman patent.
Gaffar et al in U.S. Pat. No. 5,648,064 disclose a two component whitening dentifrice in which one component is a source of active oxygen and the second component activates the bleaching activity of the first component. The two components are maintained separately until the time of application to teeth. Besides the two components, there are various inactive components added to the dentifrice composition. Among these are humectants, vehicles, surfactants, thickeners, and colorants. The colorants may be pigments or dyes and may be distributed uniformly throughout the composition or be part of a striped dentifrice. In this case, it is clear that the color moieties are present for cosmetic purposes only.
QuasarBrite, manufactured by Interdent, Inc. is advertised as a combination of 35% hydrogen peroxide with thermal absorption crystals in a translucent, semi-viscous bleaching gel. It is advertised as complementary to the Argon laser. There is no mention of color change or any other indication of process completion.
Another composition for bleaching teeth comprises aqueous hydrogen peroxide and a multiplicity of components which are combined to treat the teeth in response to the application of optical energy as disclosed by Cornell in U.S. Pat. No. 5,032,178. This patent teaches the use of a gelling agent, an accelerator, a plasticizer/thickening agent, and a means for establishing a fixed time period for treating teeth in response to the application of optical energy. A redox indicator changes from green to colorless, indicating when bleaching is complete. It also indicates if the peroxide is still powerful enough to use for bleaching. The indicator is not said to accelerate, activate or in any way enhance the bleaching ability of the peroxide.
Recent technology in the dental bleaching art includes work by Jensen et al in U.S. Pat. Nos. 5,785,527 and 5,858,332. In both of these patents, the storage stability of the activated bleaching composition is emphasized. Various other ingredients are present in the bleaching compositions to help provide consistency and potency. There is no ingredient mentioned as a color change or other visual indicator of completion of bleaching.
Smigel, in an article in the August 1996 issue of Dentistry Today discusses laser tooth whitening in detail. In this article, he mentions that hydrogen peroxide is difficult to break down and unleash its full potential for tooth whitening.
Prior to the present invention, compositions and methods for whitening teeth required a significant amount of chair time for the patient. There was also a higher cost to the dental practice in terms of special equipment, time and supplies necessary for tooth whitening.